A conventional torsion bar type torque sensor system uses a permanent magnet as a magnetic flux generator, so that residual magnetic flux density variation due to temperature variation adversely affects on sensitivity of a torque sensor. Deviation in a size, kind, and material characteristic of the permanent magnet results in fluctuation of the sensitivity and an offset value (zero point output) of the torque sensor.
The conventional torsion bar type torque sensor system is therefore equipped with a temperature sensor such as a thermistor around the permanent magnet. According to temperature detected by the temperature sensor, adjustment for the fluctuation is executed in a circuit outside the sensor.
However, the above method, so-called an external adjustment method, involves additional installment of a separated external adjustment circuit for the adjustment or enlargement of a control section of the torque sensor system when the adjustment circuit is added to the control section of the torque sensor system. This results in increasing a size and cost of the torque sensor system. Furthermore, replacement of the sensor part itself due to its breakdown invalidates previous adjustment data in the above adjustment circuit. This therefore poses replacement of the entire torque sensor system including the external adjustment circuit, which eventually increases cost in maintenance. The above problem occurs not only in the torsion bar type torque sensor system but also in a usual sensor system.